Process for extracting and purifying naturally occurring zeolite

ABSTRACT

A process for extracting and purifying naturally occurring zeolite from ores in the presence of other mineral phases by using mechanical dispersion and differential suspension to remove a majority of the clay content of the ore. The process continues by removal of contaminants with a higher mass to surface area ratio than that of the desired zeolite product by employing the properties of demineralized water in combination with a countercurrent flow separation column. No chemical flocculating or flotation agents need be employed in the process.

CROSS-REFERENCE TO RELATED APPLICATIONS

This divisional application claims priority from, and herebyincorporates by reference for all purposes, copending U.S. patentapplication Ser. No. 10/647,173, entitled Process for Extracting andPurifying Naturally Occurring Zeolite, naming Billy D. Fellers asinventor, filed Aug. 22, 2003, which is a continuation application ofU.S. patent application Ser. No. 09/672,065 (now U.S. Pat. No.6,662,951), entitled Process for Extracting and Purifying NaturallyOccurring Zeolite, naming Billy D. Fellers as inventor, filed Sep. 27,2000.

FIELD OF THE INVENTION

This invention relates to a process that provides multi-step methods ofextracting and purifying naturally occurring zeolite from zeolitic oresin the presence of other mineral phases having various properties. Morespecifically, this invention relates to a semi-continuous method forobtaining a highly enhanced, low bulk density zeolite product whichdisplays increased zeolite concentration, improved brightness, elevatedion exchange capacity, and enhanced rheological properties. The presentinvention is practiced without the use of polymeric flocculating,dispersing, or floatation materials which result in contamination of theresultant zeolite, and includes a separate step for classifying thezeolite by particle size and mineral phase.

BACKGROUND OF THE INVENTION

Natural zeolites are hydrated aluminosilicates of alkali and alkalineearth metals. Zeolites have a crystalline structure commonly known asframework aluminosilicates with infinitely extending three dimensionalnetworks of AlO₄ and SiO₄ tetrahedra linked to each other by the sharingof all oxygens. This three dimensional network structure providesextensive surface area within the zeolite, with up to 50% of zeolitevolume attributable to the channels and cavities. This propertycontributes to a specific gravity that is intermediate to other mineralphases of the natural ore, which increases the difficulty of separationsby prior art methods.

Natural zeolites are used in a variety of applications, including, forexample, ion exchange, radioactive waste treatment, industrial wastetreatment, uses as animal feed supplements, moisture absorbents,carriers for time-released substances such as pesticides or fertilizers,liquid and gas filters for contaminant and odor control, oil absorbents,and industrial coatings and fillers. Naturally occurring zeolites arealso frequently used as starting material in synthetic zeoliteproduction. Zeolites have also demonstrated usefulness as catalysts inhydrocarbon conversion reactions. The large surface area of zeolitemakes it an excellent choice for such applications.

Another feature of zeolite structure is that the cavities within aparticular zeolite are all of uniform shape and size. Consequently,natural zeolites may act as analogs to artificial molecular sieves.

One natural zeolite, clinoptilolite, possesses a particularly highabsorbing capacity due to its large surface area. Furthermore,clinoptilolite offers a high cation exchange capacity, making itsuitable for use in numerous industrial applications. The pore size ofclinoptilolite makes this zeolite well suited to waste water filtration,particularly due to its demonstrated selectivity for strategic ions.Finally, the thermal and physical stability and compatibility with finalwaste forms, such as cement or glass, make it an attractive alternativeto less stable and incompatible options such as polymer based ionexchange resins.

Naturally occurring zeolite ores are well known to contain a variety ofcontaminants, including, for example, clay, quartz, mica, feldspar, ironand titanium minerals and calcites. Naturally occurring zeolites haveheretofore been effectively excluded from certain applications whichrequire extreme brightness, such as in the fine paper industry wherehigher cost titanium dioxide, calcium carbonate or silica may bepreferred additives. Furthermore, naturally-occurring zeolites arefrequently passed over for use as molecular sieves or as catalystsbecause of ineffective purification methods.

Currently available and prior art process for extraction, purificationand classification of natural zeolites are very limited and not commonlypracticed. The art of clay minerals benificiation having been applied tozeolite ores includes pulverizing, dry classifying or wet gravitationalseparations, magnetic separation, bleaching and calcining to drive waterout of the pores has proven relatively ineffective. A number of suchprocessing techniques have been described in the prior art for zeoliteapplications, but have not been commercially successful. For example, inU.S. Pat. No. 4,510,254, a batch process is described in which azeolitic ore is processed through the steps of pulverization, slurrying,removal of fines, fine milling, magnetic separation, bleaching anddrying. The '254 process results in a dry finely ground zeolite having aparticle size of below 2 microns and a TAPPI brightness of at least 90.Zeolite obtained from the '254 process also possesses a bulk density ofabout half or less of high quality kaolin clay pigments. Despite theclaimed properties of zeolite obtained from the '254 process, naturalzeolite deposits remain difficult to treat to sufficient purity,brightness, size discrimination and density. The overall yield of '254process is less than 20% compared to greater than 40% for the presentinvention. Similarly, the zeolite content of the product obtained fromthe '254 process is slightly lower than the mineral source whereas theprocess of the present invention enhances the zeolite content by over20%. Processes according to the prior art, including the '254 patent,typically include complex chemical methods that introduce undesirablechemical contamination as part of the purification process and generatelarge waste inventories having difficult and costly treatmentrequirements. Introduction of chemical contaminants further complicatesthe prior art processes by requiring intermediate steps to amelioratethe affect of such chemical contaminants. Some prior art classificationtechniques, such as that described in U.S. Pat. No. 5,603,411, also addundesirable chemical contaminants such as flocculating agents anddispersants. Consequently, artificially produced zeolites and polymericresins remain the prime choice in high-end applications, such as ionexchange. Similarly, high cost minerals such as titanium dioxide andcalcium carbonate are preferred over zeolite in fine papermanufacturing.

The absence of natural zeolite competition in various high endapplications is largely an issue of effective and economic processes forextraction and purification from zeolite ores. There remains a needtherefore, for a process which permits economical and technicallysufficient exploitation of naturally occurring zeolite materials for abroad variety of applications. Furthermore, there is a need for aprocess which does not introduce chemical contaminants, such asflocculating or dispersing agents, and which does not produce hazardousprocess effluents.

SUMMARY OF THE INVENTION

The present invention provides an efficient, cost-effective process forthe extraction and purification of natural zeolite, from mined oreswhich include clinoptilolite and mordenite, by a novel method ofseparation from other mineral phases present in mined ores. A processhas been discovered that enables effective separation of mineral phasesby mechanical dispersal and differential suspension of respectiveminerals according to both their physical and chemical properties. Thenovel process exploits the properties of demineralized water tofacilitate differential suspension of fine particles without the use ofdispersants or other chemical suspending agents and does not includechemical flocculating agents or floatation agents that are all common tothe prior art.

The process of the present invention recognizes and exploits variationin fundamental properties of respective mineral phases including extentof hydration and influence on effective volume of particles to promotedifferential suspension. Demineralized water facilitates maximumelectrical double layer repulsion between particles and minimizes theinfluence of electrolytes on the electrical double layer to precludeflocculation.

The process of the present invention first hydrates and mechanicallydisperses the starting material to separate out the highly hydrated claycontent followed by separation of the zeolite from contaminants having ahigher mass to surface area ratio than that of the desired zeolite byuse of one or more countercurrent flow separation columns in which thedispersing medium is demineralized water.

The resulting purified product displays an increased zeoliteconcentration, improved brightness, and elevated ion exchange capacity.Further treatment with magnetic separation and fine grinding provides ahigh brightness and low bulk density product suitable for fine papercoatings and fillers in industrial whitening applications. TheTheological properties are enhanced by removal of clay and high-densityminerals. Since the residual contaminants are often near detectionlimits of the analytical method, the efficacy and mass balance are bestconfirmed in the tailings of the process where they are moreconcentrated. Existing chemical leaching techniques may further enhancethe zeolite product. However the excellent properties from the novelprocess may preclude the necessity of this expensive step for manyapplications while raising the process yield to about 59%.

The present invention further provides a new method of wetclassification of the purified zeolite stream. The wet classificationsystem of the present invention provides a significant and substantialimprovement over prior art methods of classifying fine zeolites,primarily by density difference, and also employs the properties ofdemineralized water and the electrical double layer of hydrated mineralphases to amplify their differences in settling velocity. The wetclassification method of the present invention may be applied to othertypes of fines, such as in the processing of kaolin clays, finely groundmineral ores and synthetically produced zeolites.

Overall, the present invention is much less complex than the prior artand substantially contributes to cost-effectiveness through higheryields, lower capital cost and reduction of waste liabilities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process flow diagram of the process of the presentinvention, showing an optional back end wet classification step.

FIG. 2 is a plan view of the hydration and mechanical dispersion system.

FIG. 3 is a plan view of a primary and secondary separation system.

FIG. 4 is a plan view of a wet classifying system.

DETAILED DESCRIPTION OF THE INVENTION

Referring first to FIG. 1, a process flow diagram of the process of thepresent invention, including a wet classification method, is shown. Asshown in FIG. 1, a pre-processed feedstock is hydrated and mechanicallydispersed in a first step of the present process. Once mixed withdemineralized water in this first step, the highly hydrated clayfraction of the feedstock is selectively suspended in the water. Thestable clay suspension is extracted or decanted from the hydration anddispersion tank. The hydration and mechanical dispersion is mostpreferably performed as a batch operation with one or more hydration,mixing and extracting/decanting steps preformed as mandated by thecomposition of the feedstock. Once the clay suspension is removed, theremaining feedstock fraction, which contains zeolite, is mixed withadditional demineralized water to form a slurried zeolite processstream. The slurried zeolite process stream is piped into a primaryseparation column which uses a countercurrent flow of demineralizedwater to separate the zeolite from the heavy contaminants in theslurried zeolite process stream. The zeolite exits the primaryseparation column in an overflow effluent, aided by the suspendingeffect of demineralized water, which is then passed to a secondaryseparation column. The secondary separation column also uses acountercurrent flow to further purify the overflow effluent. In contrastto the primary separation column, the lower rise rate in the secondaryseparation column removes ultra-fine particles while permitting thepurified zeolite product to drop to the bottom of the secondaryseparation column for collection. As indicated in FIG. 1, the purifiedzeolite product may be further processed by an optional wetclassification method discussed later in more detail or may be subjectedto additional size reduction.

The feedstock for the process of the present invention is a zeoliticmaterial with a mean particle size of about 10 to 40 microns. Becausethe mined zeolitic material generally possesses a particle size greaterthan 40 microns, the feedstock of the process is pre-processed to obtainthe desired average or mean particle size within the range of about 10to 40 microns. Such pre-processing may be achieved by any of a number ofknown techniques, including crushing, milling and grinding. The clayphase is substantially liberated from the ore during this feedstockpreparation and most of the liberated clay phase is reduced to aparticle size from about 10 to 100 times smaller than the bulk of thefine milled particles. The feedstock is hydrated and mechanicallydispersed, as a first step in separating and removing the clay fractionof the feedstock. This initial hydration and mechanical dispersion isconducted in a batch process and may involve one or more dispersal anddecanting procedures depending upon the initial clay load of thefeedstock.

Referring now to FIG. 2, in the preferred embodiment of the process, theclay load of the feedstock is pre-determined and sufficientdemineralized water is added through line 2 and valve 3 to suspend thehighly hydrated clay fraction of the feedstock in the batch. Mixing ofthe feedstock and demineralized water in the batch tank 15 produces aslurry. The demineralized water used possesses relatively lowelectrolyte content, typically less than about 10 to 50 ppm. It will beunderstood that demineralized water with higher electrolyte content mayalso be used; however separation efficiency may be reduced.

In contrast to prior art processes which require the addition ofchemical additives to achieve sufficient dispersal of the liberated fineclay fraction, the process of the present invention uses no suchchemical dispersants. The lack of chemical additives in the processresults in enhanced physical characteristics of the process stream,including avoidance of undispersed clay agglomerates andco-agglomeration of different mineral phases.

Generally, a slurry density of 5% to 40% is obtained in the batch tank15 with 10% to 20% being the preferred slurry density. Residence time inthe batch hydration and dispersal system, which includes batch tank 15and any recirculation streams, ranges from two to twenty-four hours andmay be adjusted according to the clay and heavies load of the feedstock.Mechanical dispersal may be achieved by use of a mixer/blender 4 or ashear pump 6, both of which are known in the art. It will be understoodthat a high density, e.g., 40% to 60%, slurry could be prepared in asemi-continuous pre-processing to the hydration and dispersal discussedherein. In the preferred embodiment of the present invention the initialhydration occurs in the batch hydration and mechanical dispersion systemwith no separate preparation of a high-density slurry. Use of such apreparation step, however, is not outside the scope of the inventiondisclosed herein. Following hydration, mechanical dispersion, andappropriate settling period the highly hydrated and stable clay phase isdecanted through line 5 with pump 6 resulting in a process stream withsubstantially less clay content. In the preferred embodiment of theprocess, the decanted zeolite product from the hydration and mechanicaldispersion step contains about 5% clay or less by weight. The separatedzeolite fraction may be used as a product in some industrialapplications or further processed as appropriate for other applications.After removal of the hydrated clay fraction, the remaining zeoliteprocess stream is slurried in the batch tank 15 with additionaldemineralized water from line 2 and valve 3 producing a slurried zeoliteprocess stream for further processing. The hydrated clay phase, removedfrom batch tank 15 via line 5 and pump 6, having about 50% clay byweight, is a potentially separate product of the novel process.

Heavy contaminants and magnetic materials may also be removed in theinitial hydration and dispersion system of the process. For example,magnetic separation may be imposed on a recirculation stream of thehydrated feedstock through lines 5, 7 a and 7 b with pump 6 and magnet 7and may be accomplished using any of a number of prior art devices andtechniques, such as those described in U.S. Pat. Nos. 3,974,067;3,990,642; 4,055,485; 4,510,254; 4,097,372; and 4,281,799.Alternatively, magnetic separation may be imposed on the slurriedzeolite process stream which is extracted from batch tank 15 throughline 9 to pump 10 and magnet 11, then on to subsequent steps in thepresent process. It will be understood that magnetic separation may alsobe used at various other points in the process of the present inventionto further extract magnetic components from the process stream. Forexample, magnetic separation may be imposed upon the overflow effluentfrom the primary separation column, which is discussed below.

Heavies may be removed in the hydration and dispersion system of thepresent process by decanting both the hydrated clay phase through line 5with pump 6 and slurried zeolite process stream using line 9 and pump10, leaving a tail fraction containing the heavies. Alternatively,heavies may be removed by under-flow or suction from the bottommostportion of the batch tank 15 at valve 13 through lines 14 a and 14 b. Itwill be understood that the mechanical dispersion to produce theslurried zeolite process stream, whether achieved through a shear pumpor a mixer/blender, the amount of water added, and recirculation of thehydration and dispersion step may be set so as to maximize heaviesremoval.

The slurried zeolite process stream may then be passed through anoptional centrifugal separation 12 to remove additional heavy wastematerials, such as quartz. This step may be bypassed or eliminateddepending upon the heavy load of the feedstock. Furthermore, it will beunderstood that the need for additional heavies removal may depend uponthe efficacy of any heavies removal undertaken in the hydration anddispersion system.

Referring to FIG. 3, the slurried zeolite process stream is passed to aprimary separation column 16. The primary separation column 16 utilizesdistinct flow rates in conjunction with specific separation zones toseparate and remove high density contaminants having limited surfacearea and minimal influence of demineralized water. A counterflow is usedto suspend and to maintain the suspension of the higher surface areazeolite in the slurried zeolite process stream.

Still referring to FIG. 3, the slurried zeolite process stream is fedinto the primary separation column 16 at approximately the midpoint ofthe column through line 22. Line 22 terminates in a nebulizing nozzle 22a which reduces the velocity and turbulent effect of the slurriedzeolite process stream downward into an ascending demineralized waterstream. The demineralized water stream arises from a feed ofdemineralized water into the lower portion of the primary separationcolumn 16 through line 25. The primary separation column utilizes thevariation in hydrating properties and mass to surface area ratiosbetween the desired zeolite particles and clay contaminants as well asthe additional affects of the electrical double layer to separate thezeolite from clay contaminant. That is, separation in the primaryseparation column is not solely a hydraulic effect. The demineralizedwater leaves the electrical double layer intact and there is an addedseparation effect due to the surface interactions between the electricaldouble layer on the surface of the particles and the demineralizedwater. Prior art hydraulic separation process, such as that discussed inU.S. Pat. No. 4,554,066, rely on high mass to surface area ratiostypical of larger particles and in which the effects of the electricaldouble layer are negligible in comparison to hydraulic effects. Wheresuch ratios are high, there is no separation benefit from surfaceinteractions with the electrical double layer. In the present process,the particles do not have such high mass to surface area ratios and sothe effect of the electrical double layer is not insignificant incomparison to the hydraulic effect. Once separated, the zeoliteparticles are suspended and passed through the upper stage 28 of theprimary separation column 16 until they are removed through the overflowpipe 29 of the primary separation column 16. The upward flow in theprimary separation column is less than would be required to suspend theheavies in the slurried zeolite process stream. The amount and rate ofthe added demineralized water and the upward flowrate of the water mayvary depending upon the initial feedstock composition, the efficacy ofupstream separations, the mean particle sizes of the zeolite andcontaminants and the overflow extraction rate. As can be seen in FIG. 3,a mid-stage 23 of the column is larger in diameter than the upper stage28 and lower stage 24 of the column 16. Such a larger diameter stage isoften referred to as an expansion stage. The major part of theseparation of the zeolite from the heavies in the slurried zeoliteprocess stream occurs in the mid-stage 23. A transparent lower stage 24is used to visually determine the efficacy of the separation in theprimary separation column 16.

The flow of demineralized water may be controlled by a manual controlvalve 26 and monitored by flowmeter 27. It will be understood thatalthough a manual operation is illustrated in FIG. 3, operation of theprimary separation column 16 may be automated with currently availableprocess control equipment. Similarly, the efficacy of separation by theprimary separation column 16 may be determined automatically withcurrently available analytical equipment and techniques. For example,the overflow effluent from the primary separation column 16 exitingthough overflow pipe 29 may be analyzed for particle size, density,and/or mineral content. If such analysis shows that an unacceptablelevel of heavy contaminants is being carried into the overflow effluent,the rate of demineralized water addition and overflow effluentextraction may be altered.

Referring still to FIG. 3, it can be seen that primary separation column16 is capped by a cap 33 and that overflow pipe 29 lies immediatelybelow cap 33. The resulting overflow effluent contains a zeolite productwhich may be collected through valve 54 and dewatered and dried forindustrial applications. Alternatively, the overflow effluent of primaryseparation column 16 may be subjected to additional wet processingtechniques, as discussed below, for specific product refinement.

Referring still to FIG. 3, undesirable heavy contaminants, includingmost typically, quartz, opal and iron, are removed through line 31 andvalve 30. Additional water may be added to the heavy contaminant streamthrough line 32 a and valve 32 to lower the viscosity of the heavycontaminant stream to assist in its removal. It will be understood thatthe heavy contaminant stream removed through valve 30 may be disposed ofor recycled back through the primary separation column 16 through line25 and valve 26 to recover any remaining zeolite content.

As seen in FIG. 3, additional wet processing of the overflow effluentfrom primary separation column 16 may be undertaken by passing theoverflow effluent into a secondary separation column 17 through line 40which terminates in one or more nebulizers 41 which are positioned atabout the midpoint of the secondary separation column 17. Therein, thezeolite product is exposed to a final fines wash by the counterflowdemineralized water entering through a flow distributor 43 at the baseof the secondary separation column 17 through valve 44. The flow ofdemineralized water entering through valve 44 may be monitored by aflowmeter 45. Residual clay, mica, or other fine contaminants rise andpass through the overhead stream through overhead pipe 46 of thesecondary separation column 17. The purified zeolite product iscollected as an underflow effluent through line 47 and valve 48 ineither a batch or continuous mode of transfer.

Additional wet classification of the underflow effluent from secondaryseparation column 17 may be undertaken to further separate the zeoliteby particle size. FIG. 4 illustrates a multiple wet classifier system ofone embodiment of the process of the present invention.

In one operational mode, underflow effluent from secondary separationcolumn 17 is passed through line 47 a and is transferred, with optionalparticle size reduction at 75, to suspension vessel 49 and combined withdemineralized water injected through line 50 a and valve 50. Again, theflow of demineralized water through valve 50 may be monitored with aflowmeter 51. A slurry is established in suspension vessel 49 using arecirculation-feed pump 53 through lines 52 and 54, and valve 55 a.Forward feed to the wet classification system proceeds through line 55,which terminates in nebulizer 56 at about the midpoint of firstclassifying column 77, and regulating valve 64 to provide the desiredflow rate at flowmeter 65, introduced into about the midpoint of thefirst wet classifying column 77.

In a second operational mode, overflow effluent from primary separationcolumn 16 bypasses the secondary separation column and is passed to thewet classification system. In such second operational mode, overfloweffluent from primary separation column 16 is injected into a first wetclassifying column 77 through line 55 valve 64 and flowmeter 65.

First wet classifying column 77 utilizes distinct flow rates inconjunction with specific separation zones to separate the zeolitecontent by particle density, mineral phase and/or size. As shown in FIG.4, first stage column 77 possesses an upper stage 68 a, a midstage 63 aand a lower stage 64 a. Referring still to FIG. 4, the midstage 63 a islarger in circumference than the upper stage 68 a and lower stage 64 a.Demineralized water is added, to amplify differences in particlesettling velocity, to column 77 through pipe 65 a being controlled atvalve 66 a and measured at flowmeter 67 a to provide a flowcountercurrent to descending zeolite in column 77. Column 77 is cappedby cap 72 a. The overflow effluent from column 77 is extracted throughoverflow pipe 69 a and into pipe 80. Heavier and/or larger zeoliteparticles and any remaining heavy contaminants exit first classifyingcolumn 77 as underflow through pipe 71 a and valve 71 b which is locatedat or near the bottommost portion of column 77.

Referring still to FIG. 4, the overflow effluent from first classifyingcolumn 77 may be further processed by passage into about the midpoint ofa second classifying column 78 through pipe 80, which terminates innebulizer 81. Second classifying column 78 utilizes distinct flow ratesin conjunction with specific separation zones to further separate thezeolite by particle size and/or mineral phase. Demineralized water isintroduced into second classifying column 78 through pipe 66 within alower stage 64 b of second classifying column 78. Second classifyingcolumn 78 is capped by cap 72 b and the overflow from column 78 exitsthrough overflow pipe 69 b. Smaller zeolite particles present in theoverflow effluent from first classifying column 77 and injected intosecond classifying column 78 are suspended by a countercurrent stream ofdemineralized water and carried through an upper stage 68 b to pipe 69b. Heavier or larger zeolite particles present in the overflow effluentfrom first classifying column 77 may be withdrawn from the bottom ofsecond classifying column 78 through pipe 71 and valve 71 b.

It will be understood that, as an alternative to further classification,all or a portion of the overflow effluent from first classifying column77 may be collected and dried for end use or may be further processed bymilling, magnetic separation or chemical leaching. Similarly, all orpart of the overflow effluent from second classifying column 78 may becollected and dried for end use or may be further classified usingadditional classifying columns possessing finer separation properties,such as longer expansion zones or otherwise processed.

Although FIG. 4 illustrates a two column wet classification system, itwill be understood that the number, sizes and configurations of the wetclassifying columns may vary depending upon the extent and exactness ofseparation by particle size and/or mineral phase desired. That is, thenarrower the range of particle size classification desired, the greaterthe number and/or size of classifying columns required. As with theprimary separation column 16, the amount and rate of demineralized wateraddition and subsequent upward flowrate is dependent upon the particlesize and/or desired yield of the overflow effluent, the particle sizerange of the process stream fed into the column, and the overflowextraction rate. It will be further understood that although theslurried zeolite process stream is prepared as a batch process in thepreferred embodiment of the present invention, all subsequent steps inthe present process may be run semi-continuously. The wet classificationtechnique disclosed herein has not heretofore been applied in theprocessing of clay materials, in general, or of naturally occurringzeolites, in particular, and is a significant and substantialimprovement over prior art methods as no other zeolite classifyingtechnique has approached this level of zeolite enrichment and concurrentwith particle size classification. As with the primary separationcolumn, the wet classification method of the present invention reliesupon the separation effect of the intact electrical double layer.

Each of the separation zones and capacities of primary separation column16 and each of first and second classifying columns 77 and 78,respectively, may be regulated not only by the size and configurationsof such columns but also by one or more downstream pumps. The componentequipment, i.e., batch tanks, columns, piping, valves, meters, in-lineprobes and pumps, may be made from any of a variety of materialsincluding glass, plastics, such as polyvinylchloride (“PVC”), and metaland metal alloys. Because the process does not utilize high temperaturesor corrosive chemicals, cheaper materials of construction, such as PVC,may be used.

It will be recognized that all steps of the novel process are performedwith demineralized water, absent chemical additives, as a commonsuspension fluid and may be conducted in series and without eitherneutralizing chemical treatments or rinsing operations to remove achemical background, as required of prior art methods.

The preparations of demineralized water for use in the process of thepresent invention can be accomplished by various methods in common use.By way of example, a water source having in excess of 1500 ppm totalelectrolytes may be processed using a combination of filtration, reverseosmosis and ion exchange steps.

It was unexpectedly discovered that the electrolyte content of someprocess effluents, particularly after the initial clay removal step,remained remarkably low and allowed the option of recycle by minimaltreatment by filtration and ion exchange and to substantially restorethe original quality. The absence of chemical additives, common toprocesses of the prior art, was a principal factor in feasibility andeconomic treatment of water effluent from the novel process. Thisdemonstrated that the economic advantage of the process could beenhanced not only by the recycle but also by avoidance of largeinventories of wastewater common to the prior art methods. This reducesdemand on water resources, particularly in areas of limited supplies.Therefore, the preferred embodiment substantially adds to both theeconomic and environmental advantages of the novel process, as well asthe overall process performance.

The process of the present invention is further illustrated by referenceto the examples below.

EXAMPLE 1

Bench Scale Demonstration of the Novel Process Batch Clay SeparationStep

A 15 lb batch of zeolite ore containing 45% clinoptilolite, 20%mordenite, 15% feldspar, 10% clay, 5% mica and 5% quartz was pulverizedto a mean particle size of approximately 11 microns. The materialprovided a TAPPI brightness of 72.7, a cation exchange capacity of 1.10meq/g, and a FeO concentration of 1.20%. The pulverized ore was mixedwith 7.9 gallons of demineralized water, having less than about 10 ppmelectrolytes, to form a slurry of 23% solids. The slurry was mixed in abatch fashion using a blender at high speed for 10 minutes per batch.The dispersed slurry was distributed into 5-gallon containers andallowed to settle for 24 hours. Following the settling period, the clayliquid suspension was decanted from the settled slurry providing 12.8lbs of zeolite solids remaining in the containers, which provided ayield of 85% for this step.

Analysis of the material from the clay liquid suspension indicated thatit consisted of 50% clay, 25% clinoptilolite, 15% feldspar, 5%mordenite, and 5% quartz with a FeO concentration of 2.97%. It alsodemonstrated a TAPPI brightness of 61.3 and a cation exchange capacityof 0.78 meq/g.

Analysis of the zeolite material provided 55% clinoptilolite, 15%mordenite, 15% feldspar, 5% clay, 5% mica, and 5% quartz. The materialprovided a TAPPI brightness of 72.0, a cation exchange capacity of 1.21meq/g, and a FeO concentration of 0.66%.

Continuous Primary Separator Step

The zeolite solids were transferred to a 25-gallon tank and mixed with15.4 gallons of demineralized water to form a 10% slurry. The slurry wasmixed by recirculation with a submersible sump pump, which was attachedto a bench scale version of the system described in FIG. 3. A counterflow of demineralized water, having less than about 10 ppm electrolytes,was introduced at the base of the separator column to provide a riserate of 4.3 milliliters per minute per square centimeter in the lowersection of the column. Feed from the slurry tank to the column wasinitiated to establish a rise rate of 3.8 milliliters per minute persquare centimeter in the injection zone of the column. The entire slurryvolume was pumped to the column, then the feed was secured and thecounter flow demineralized water was balanced to maintain the standardrise rates for an additional 12 hours.

Approximately 1 lb of discard material was collected at the bottom ofthe column as underflow concentrate. Analysis of this material indicatedthat it consisted of 35% quartz, 25% feldspar, 15% clinoptilolite, 10%mordenite, 5% clay, 5% mica, and 5% hematite with a FeO concentration of1.66%. It also demonstrated a cation exchange capacity of 0.66 meq/g anda TAPPI brightness of 53.7.

The final purified zeolite product collected in the secondary separationcolumn totaled 11.5 lbs., which provided a yield of 90% for this step.This material consisted of 55% clinoptilolite, 15% mordenite, 15%feldspar, 5% clay and 5% quartz with a FeO concentration of 0.55%. Italso demonstrated a cation exchange capacity of 1.22 meq/g and a TAPPIbrightness of 71.5.

Magnetic Separation Step

The purified zeolite product was mixed with 7.6 gallons of demineralizedwater, having less than about 10 ppm electrolytes, to form a 20% slurry.The slurry was manually treated with rare earth magnets (6 kG) in astatic soak system. A total of 1 lb of magnetic material was extractedfrom the zeolite leaving 10.5 lbs. of purified material, which is ayield of 91% for this step. The material provided a 86.0 TAPPIbrightness, a cation exchange capacity of 1.33 meq/g, and a FeOconcentration of 0.31%. Mineral analysis of the material indicated thatit consisted of 60% clinoptilolite, 20% mordenite, 15% feldspar, and 5%quartz (clay and mica less than detectable).

Particle Size Reduction Step

A 6.9 lb portion of the magnetically separated zeolite was ground dry toa mean particle size of approximately 3 microns using a model 4micro-jet system from Fluid Energy Aljet. The ground product provided a90.5 TAPPI brightness, a cation exchange capacity of 1.26 meq/g, and aFeO concentration of 0.31%. SUMMARY OF PROCESSING CEC Brightness SampleZeolite % meq/g TAPPI FeO % Feed Ore 65 1.10 72.7 1.20 Decanted Zeolite70 1.21 72.0 0.66 Clay Liquid Suspension 25 0.78 61.3 2.97 PrimarySeparator 25 0.66 53.7 1.66 Secondary Separator 70 1.22 71.5 0.55Magnetic Treatment 80 1.33 86.0 0.31 3 micron Product 80 1.26 90.5 0.31

EXAMPLE 2

Pilot Scale Demonstration of the Novel Process Batch Clay SeparationStep

A 180 lb batch of zeolite ore containing 45% clinoptilolite, 20%mordenite, 15% feldspar, 10% clay, 5% mica and 5% quartz was pulverizedto a mean particle size of approximately 12 microns. The materialprovided a TAPPI brightness of 72.0, a cation exchange capacity of 1.11meq/g, and a FeO concentration of 1.29%. The pulverized ore was mixedwith 86 gallons of demineralized water, having less than about 50 ppmelectrolyte, in a tank to form a slurry of 20% solids. The slurry wasmixed with rapid agitation using a Chemineer (model 5JTC) tank mixer forone hour. Mixing was then stopped and the slurry was allowed to settlefor 24 hours. Following settling, the liquid phase was decanted from thetank using a submersible sump pump. The separated zeolite productremaining in the tank totaled 151 lbs., which provided a 83% yield.

Analysis of the material from the clay liquid suspension indicated thatit consisted of 50% clay, 25% clinoptilolite, 15% feldspar, 5%mordenite, and 5% quartz with a FeO concentration of 2.97%.

Analysis of the zeolite material provided 55% clinoptilolite, 15%mordenite, 15% feldspar, 5% clay and 5% quartz. The material provided aTAPPI brightness of 72.0, a cation exchange capacity of 1.21 meq/g, anda FeO concentration of 0.66%.

Continuous Primary Separator Step

The separated zeolite product remaining in the tank, from the proceedingstep, was mixed with 160 gallons of demineralized water, having lessthan about 50 ppm electrolyte, to form a 10% slurry. The slurry wasmixed with rapid agitation using the Chemineer tank mixer for 10minutes. The mixer was removed and the submersible sump pump wasreturned to the tank for internal recirculation. A small slipstream waspassed over a reduced scale rare earth magnet solely to demonstratefeasibility of effective removal of magnetic material at this step ofthe process.

A second submersible sump pump was placed in the tank and connected to apilot scale separation column based on the design described in FIG. 3.Demineralized water, having less than about 50 ppm electrolyte, wasdelivered to the column base to provide a rise rate of 4.3 millilitersper minute per square centimeter in the lower section of the column.Zeolite slurry feed was initiated to the column with the sump pump toestablish a rise rate of 3.8 milliliters per minute per squarecentimeter in the injection zone of the column. Demineralized water flowwas also established at the secondary separation column distributionring to provide a rise rate of 0.5 milliliters per minute per squarecentimeter. Following the addition of the contents of the slurry tank tothe primary column, demineralized water was continued at the column baseand secondary separation column distribution ring, maintaining thestandard rise rates, for an additional 12 hours. The final yield ofpurified zeolite product was 134 lbs., which provided a yield of 89% forthis step. Analysis of the zeolite product provided 65% clinoptilolite,15% mordenite, 10% feldspar, 5% mica, and 5% quartz (clay less thandetectable). The material provided a TAPPI brightness of 67.0, a cationexchange capacity of 1.33 meq/g, and a FeO concentration of 0.68%.

Approximately 29 lbs. of discard material was collected at the bottom ofthe column as underflow concentrate. Analysis of this material indicatedthat it consisted of 35% quartz, 25% feldspar, 15% clinoptilolite, 10%mordenite, 5% clay, 5% mica, and 5% hematite with a FeO concentration of1.66%. It also demonstrated a cation exchange capacity of 0.66 meq/g anda TAPPI brightness of 53.7.

Magnetic Separation Step 1

A 143 lb. sample of purified zeolite product from the column system wasslurried with 28 gallons of demineralized water to 38% solids and mixedwith a standard drum mixer. The slurry was subjected to magneticseparation by passing it through a Pacific Electric Motor Company (PEM)high intensity (20 kG) wet magnetic separator equipped with a 5 inchdiameter canister filled with expanded metal at 3 gallons per minute (30second retention). The entire volume of slurry was passed through themagnet two times during the treatment. Analysis of the material provideda TAPPI brightness of 77.7 and a FeO concentration of 0.50%.

Particle Size Reduction Step

The product from the magnetic separation was then subjected to particlesize reduction using a Chicago Boiler Red Head attrition mill equippedwith one-millimeter glass beads at a flow rate of one gallon per-minute.Four passes through the mill were required to achieve a particle size ofless than 2 microns. The milled product was then screened with a200-mesh screen to remove stray grinding media and mill wear products.Analysis of the material demonstrated a TAPPI brightness of 84.0 and aFeO concentration of 0.35%.

Magnetic Separation Step 2

The attrition mill product was subjected to magnetic separation again bypassing it through the PEM high intensity (2 tesla) wet magneticseparator equipped with a 5 inch diameter canister filled with stainlesssteel wool at 1 gallon per minute (100 second retention). The entirevolume of slurry was passed through the magnet two times during thetreatment. The final product was estimated to 106 lbs. in the form of a17% solids slurry. This provided a zeolite product yield of 74%. Asample of the dried material displayed a TAPPI brightness of 89.9, a FeOconcentration of 0.32 and a particle size of less than 2 microns.SUMMARY OF PROCESSING SAMPLE Zeolite CECError Brightness FeO Feed Ore 651.33 66.7 1.27 Decanted Zeolite 70 1.43 66.4 0.71 Clay Liquid Suspension40 0.81 61.3 2.97 Primary Separator Underflow 40 0.66 53.7 1.66Secondary Separator Product 80 1.45 66.2 0.68 Pass 1 Magnetic Separation73.8 0.58 Pass 2 Magnetic Separation 77.7 0.50 Attrition Mill Product84.0 0.35 Pass 3 Magnetic Separation 89.1 0.31 Pass 4 MagneticSeparation 1.70 89.9 0.32

EXAMPLE 3

Bench Scale Demonstration of Classifier Process

Five bench scale columns based on the design described in FIG. 4 wereconnected in series. Rise rates were established in the lower sectionsof the first and second columns with counter flow demineralized water at0.99, and 0.22 milliliters per minute per square centimeter. A sample ofzeolite product from the primary separator column was slurried to 10%solids with demineralized water, having an electrolyte content of lessthan about 10 ppm. The slurry was fed to the first column to establish arise rate within the injection zone of 0.86 milliliters per minute persquare centimeter and subsequent columns having slightly reduced riserates. The entire slurry volume was pumped to the classifier, then feedwas secured and the counter flow at the column bases was maintained for12 hours.

The material that settled out at the bottom of each column was collectedas underflow and analyzed. The data is summarized below: ANALYSIS OFCLASSIFIER SYSTEM PRODUCTS Sample Mass FeO (%) Apparent Density (g/ml)Primary Separator Product — 0.66 0.89 Column 1 Product 59 0.86 0.86Column 2 Product 22 0.67 0.82 Column 3 Product 11 1.04 0.79 Column 4Product 7 1.07 0.75 Column 5 Product 1 2.56 0.73

The data reflects linear reduction of apparent density from about 0.86g/ml to about 0.73 g/ml from which a linear particle size reduction isinferred from about 8.2 to 6.5 microns or about 0.5 microns for eachclassifier column. The enhanced iron content, especially column 5,reflects further separation of trace residual clays or other ironcontaining minerals.

EXAMPLE 4

Bench Scale Demonstration of Classification Process

Five bench scale columns based on the design described in FIG. 4 wereconnected in series. Rise rates were established in the lower sectionsof the first and second columns with counter flow demineralized water at1.5, and 0.35 milliliters per minute per square centimeter. A sample ofzeolite product from the particle size reduction step of Example 1(i.e., 3 micron Product) was slurried to 10% solids with demineralizedwater, having an electrolyte content of less than about 10 ppm. Theslurry was fed to the first column to establish a rise rate within theinjection zone of 0.88 milliliters per minute per square centimeter andsubsequent columns having slightly reduced rise rates. The entire slurryvolume was pumped to the classifier, then feed was secured and thecounter flow at the column bases was maintained for 12 hours.

The material that settled out at the bottom of each column was collectedas underflow and analyzed. The data is summarized below: ANALYSIS OFCLASSIFIER SYSTEM PRODUCTS Sample Mass FeO (%) CEC Apparent Density FeedProduct — 0.25 1.35 — Column 1 Product  7 0.19 1.03 1.08 Column 2Product 11 0.16 1.31 0.92 Column 3 Product 32 0.23 1.51 0.78 Column 4Product 26 0.22 1.53 0.72 Column 5 Product 24 0.36 1.46 0.60

The data reflects linear reduction of apparent density from about 1.08g/ml to 0.6 g/ml from which is inferred a linear and relatively smallaverage particle size difference. The iron distribution reflects furtherseparation from the zeolite in columns 1 through 4 and enhancement inthe column 5 product, reflecting further separation of trace residualclays or other iron containing minerals. The cation exchange capacityrevealed collection of a small fraction of zeolite depleted mineral incolumn 1 and significant enhancement in columns 3 and 4 and somewhatlesser extent in column 5. This distribution clearly demonstratedbeneficial separation concurrent with particle size classification.Composite sample of columns 3 and 4 provided a 91.2 TAPPI brightnesscompared to the feed product having a TAPPI brightness of 90.5.

The present invention is set forth herein in terms of specificembodiments thereof. However, it will be understood in view of thedisclosure contained herein that one of ordinary skill in the art isenabled to practice numerous variations of the invention. Suchvariations are within the scope of the disclosure herein. Consequently,the invention is to be broadly construed and limited only by the scopeand spirit of the claims appended hereto.

1-55. (canceled)
 56. A method for classification of a particulatemineral compound comprising: injecting demineralized water into one ormore countercurrent classifying columns comprising an aqueous slurry ofthe particulate mineral compound to form an ascending demineralizedwater stream sufficient to amplify differences in particle settlingvelocity.
 57. The method of claim 56, wherein the one or moreclassifying columns each have one or more stages, a feed injection portat about the midpoint of said classifying column, a demineralized waterinjection port below said feed injection port, a cap at such column'stopmost edge, and an overflow port below said cap.
 58. The method ofclaim 56, wherein the number, size and/or configuration of the one ormore countercurrent classifying columns is tailored to a desiredparticle size and/or mineral phase.
 59. The method of claim 56, whereinthe aqueous slurry in the countercurrent classifying column has a slurrydensity of about 5% to about 40%.
 60. The method of claim 56, whereinthe particulate mineral compound comprises particles possessing anelectrical double layer when hydrated in low electrolyte medium andhaving a range of particle sizes.
 61. The method of claim 56, whereinsaid particulate mineral compound is a compound comprising particles ofa desired range of sizes from a lower portion of a secondary separationcolumn.
 62. The method of claim 56, wherein the particulate mineralcompound is a zeolite compound.
 63. The method of claim 56, wherein theaqueous slurry has a slurry density of 10% to 20%.
 64. The method ofclaim 56, wherein the demineralized water has a low electrolyte content.65. The method of claim 56, wherein the demineralized water has anelectrolyte content of less than about 500 ppm.
 66. The method of claim56, wherein the demineralized water has an electrolyte content of lessthan about 100 ppm.
 67. The method of claim 56, wherein thedemineralized water has an electrolyte content of less than about 50ppm.
 68. The method of claim 56, wherein the demineralized water has anelectrolyte content of less than about 10 ppm.
 69. A method forclassification of a particulate mineral compound comprising: introducingan aqueous slurry of said particulate mineral compound slurry into acountercurrent classifying column, said classifying column having one ormore stages, a feed injection port at about the midpoint of saidclassifying column, a demineralized water injection port below said feedinjection port, a cap at such column's topmost edge, and an overflowport below said cap; injecting demineralized water into saidcountercurrent classifying column at said demineralized water injectionport so as to form an ascending demineralized water stream sufficient toamplify differences in particle settling velocity; separating saidparticulate compound using the separation effect of said electricaldouble layer; and extracting an overflow stream through said overflowport.
 70. The method of claim 69, wherein said particulate mineralcompound is a compound comprising particles of a desired range of sizesfrom a lower portion of a secondary separation column.
 71. The method ofclaim 69, wherein the particulate mineral compound is a zeolitecompound.
 72. The method of claim 69, wherein the aqueous slurry in thecountercurrent classifying column has a slurry density of about 5% toabout 40%.
 73. The method of claim 69, wherein the aqueous slurry in thecountercurrent classifying column has a slurry density of about 10% toabout 20%.
 74. The method of claim 69, wherein the demineralized waterhas a low electrolyte content.
 75. The method of claim 69, wherein thedemineralized water has an electrolyte content of less than about 500ppm.
 76. The method of claim 69, wherein the demineralized water has anelectrolyte content of less than about 100 ppm.
 77. The method of claim70, wherein the demineralized water has an electrolyte content of lessthan about 50 ppm.
 78. The method of claim 71, wherein the demineralizedwater has an electrolyte content of less than about 10 ppm.
 79. A methodfor classification of a particulate mineral compound comprising:injecting a slurried process stream into a multistage countercurrentprimary separation column at about the midpoint of said primaryseparation column, said primary separation column having upper, lowerand mid-stages; injecting demineralized water into said lower stage ofsaid primary separation column; extracting an overflow stream ofsuspended particulate mineral compound from said upper stage of saidprimary separation column; and controlling the injection rate of saidslurried process stream and said demineralized water into said primaryseparation column and the extraction rate of said suspended particulatemineral compound such that said demineralized water flows upward at arate sufficient to suspend said particulate compound and such thathigher density components of said slurried process stream, having a netsettling velocity, flow downward to said lower stage of said primaryseparation column.
 80. The method of claim 79, additionally comprising:injecting said suspended particulate mineral compound from said primaryseparation column into a secondary separation column, said secondaryseparation column having upper and lower portions; injectingdemineralized water into said secondary separation column near saidlower portion; extracting a fine particle overflow stream from saidupper portion; controlling the injection rates of said suspendedparticulate mineral compound and said demineralized water into saidsecondary separation column and the extraction rate of said fineparticle overflow stream such that a countercurrent flow is establishedand that particles of said particulate mineral compound of a desiredrange of sizes are not carried into said countercurrent flow; andremoving said particles of a desired range of sizes from said lowerportion of said secondary separation column. 81-93. (canceled)